Catheter having mapping assembly

ABSTRACT

A mapping catheter comprises a catheter body and a mapping assembly. The catheter body has an outer wall, proximal and distal ends, and at least one lumen extending therethrough. The mapping assembly comprises a generally straight proximal region attached to the catheter body, a generally circular main region distal the proximal region having an outer circumference, and a generally straight distal region distal the main region. The mapping assembly also comprises a support member having shape-memory, a non-conductive covering over the support member, and a plurality of electrodes on the non-conductive covering along the generally circular main region.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of U.S. application Ser. No.10/075,803, filed Feb. 11, 2002, entitled CATHETER HAVING MAPPINGASSEMBLY, which is a divisional of U.S. application Ser. No. 09/551,467,filed Apr. 17, 2000, which claims the benefit of U.S. ProvisionalApplication No. 60/178,478, filed Jan. 27, 2000, the disclosures ofwhich are incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to an improved mapping catheterthat is particularly useful for mapping electrical activity in a tubularregion of or near the heart.

BACKGROUND OF THE INVENTION

[0003] Atrial fibrillation is a common sustained cardiac arrythmia and amajor cause of stroke. This condition is perpetuated by reentrantwavelets propagating in an abnormal atrial-tissue substrate. Variousapproaches have been developed to interrupt wavelets, including surgicalor catheter-mediated atriotomy. Prior to treating the condition, one hasto first determine the location of the wavelets. Various techniques havebeen proposed for making such a determination. None of the proposedtechniques, however, provide for measurement of the activity within apulmonary vein, coronary sinus or other tubular structure about theinner circumference of the structure.

SUMMARY OF THE INVENTION

[0004] The present invention is directed to a catheter having a mappingassembly and a method for measuring electrical activity within a tubularregion of or near the heart, e.g., a pulmonary vein, the coronary sinus,the superior vena cava, or the pulmonary outflow tract. The mappingassembly, which has a generally circular region with a series ofspaced-apart electrodes mounted thereon, is positioned within thetubular region so that the electrodes are in contact with an innergenerally circumferential surface inside the tubular structure.

[0005] In one embodiment, the invention is directed to a mappingcatheter comprising an elongated tubular catheter body and a mappingassembly mounted at the distal end of the catheter body. The catheterbody has an outer wall, proximal and distal ends, and at least on lumenextending therethrough. The mapping assembly comprises a tubularstructure having a generally straight proximal region attached to thecatheter body, a generally circular main region generally transverse anddistal to the proximal region having an outer circumference, atransition region connecting the proximal region and the main region,and a generally straight distal region distal the main region,preferably extending substantially tangentially to the generallycircular main region of the mapping assembly. The assembly furthercomprises a support member having shape-memory disposed within at leastthe main region of the mapping assembly. A plurality of spaced-apartelectrodes are carried by the generally circular main region of themapping assembly.

[0006] In another embodiment, the invention is directed to a method formapping electrical activity within a tubular region of or near theheart, wherein the tubular region has an inner generally circumferentialsurface. The method comprises inserting the distal end of a catheter asdescribed above into the heart. The outer circumference of the generallycircular main region of the mapping assembly is contacted with the innergenerally circumferential surface of the tubular region. The electricalactivity within the tubular region is mapped with the electrodes of thegenerally circular main region. The method is particularly useful formapping tubular regions such as pulmonary veins, the coronary sinus, thesuperior vena cava, and the pulmonary outflow tract.

DESCRIPTION OF THE DRAWINGS

[0007] These and other features and advantages of the present inventionwill be better understood by reference to the following detaileddescription when considered in conjunction with the accompanyingdrawings wherein:

[0008]FIG. 1 is a side cross-sectional view of an embodiment of thecatheter of the invention;

[0009]FIG. 2 is a side cross-sectional view of a catheter body accordingto the invention, including the junction between the catheter body andintermediate section;

[0010]FIG. 3 is a cross-sectional view of the intermediate section;

[0011]FIG. 4 is a schematic perspective view of the mapping assemblyaccording to the invention;

[0012]FIG. 5 is a side view of the mapping assembly according to theinvention in a clockwise formation;

[0013]FIG. 6 is a side view of the mapping assembly according to theinvention in a counterclockwise formation rotated 90° relative to theassembly depicted in FIG. 5;

[0014]FIG. 7 is a schematic view of the mapping assembly according tothe invention; and

[0015]FIG. 8 is a schematic view of the mapping assembly according tothe invention depicting the relationship between the first and lastelectrodes.

DETAILED DESCRIPTION

[0016] In a particularly preferred embodiment of the invention, there isprovided a catheter having a mapping assembly at its distal end. Asshown in FIG. 1, the catheter comprises an elongated catheter body 12having proximal and distal ends, an intermediate section 14 at thedistal end of the catheter body, a control handle 16 at the proximal endof the catheter body, and a mapping assembly 17 mounted at the distalend of the catheter to the intermediate section.

[0017] With reference to FIG. 2, the catheter body 12 comprises anelongated tubular construction having a single, axial or central lumen18. the catheter body 12 is flexible, i.e., bendable, but substantiallynon-compressible along its length. The catheter body 12 can be of anysuitable construction and made of any suitable material. A presentlypreferred construction comprises an outer wall 20 made of polyurethaneor PEBAX. The outer wall 20 comprises an embedded braided mesh ofstainless steel or the like to increase torsional stiffness of thecatheter body 12 so that, when the control handle 16 is rotated, theintermediate section 14 of the catheter 10 will rotate in acorresponding manner.

[0018] The outer diameter of the catheter body 12 is not critical, butis preferably no more than about 8 french, more preferably about 7french. Likewise, the thickness of the outer wall 20 is not critical,but is thick enough so that the central lumen 18 can accommodate apuller wire, lead wires, and any other desired wires, cables or tubes.If desired, the inner surface of the outer wall 20 is lined with astiffening tube (not shown) to provide improved torsional stability. Aparticularly preferred catheter has an outer wall 20 with an outerdiameter of from about 0.090 inch to about 0.94 inch and an innerdiameter of from about 0.061 inch to about 0.065 inch.

[0019] The intermediate section 14 comprises a short section of tubing22 having three lumens. The first lumen 30 carries electrode lead wires50, the second lumen 32 carries a puller wire 64, and the third lumen 34carries a support member 24. The tubing 22 is made of a suitablenon-toxic material that is preferably more flexible than the catheterbody 12. A presently preferred material for the tubing 22 is braidedpolyurethane, i.e., polyurethane with an embedded mesh of braidedstainless steel or the like. The size of each lumen is not critical, butis sufficient to house the lead wires, puller wire or support member.

[0020] The useful length of the catheter, i.e., that portion that can beinserted into the body excluding the mapping assembly 17, can vary asdesired. Preferably, the useful length ranges from about 10 cm to about120 cm. the length of the intermediate section 14 is a relatively smallportion of the useful length and preferably ranges from about 3.5 cm toabout 10 cm, more preferably from about 5 cm to about 6.5 cm.

[0021] A preferred means for attaching the catheter body 12 to theintermediate section 14 is illustrated in FIG. 2. The proximal end ofthe intermediate section 14 comprises an outer circumferential notch 26that receives the inner surface of the outer wall 22 of the catheterbody 12. The intermediate section 14 and catheter body 12 are attachedby glue or the like.

[0022] If desired, a spacer (not shown) can be located within thecatheter body between the distal end of the stiffening tube (ifprovided) and the proximal end of the intermediate section. The spacerprovides a transition in flexibility at the junction of the catheterbody and intermediate section, which allows this junction to bendsmoothly without folding or kinking. A catheter having such a spacer isdescribed in U.S. Pat. No. 5,964,757, the disclosure of which isincorporated herein by reference.

[0023] At the distal end of the intermediate section 14 is a mappingassembly, as shown in FIGS. 3 to 7. The mapping assembly is formed fromthe distal end of the support member 24 covered by a non-conductivecovering 28. The mapping assembly comprises a generally straightproximal region 38, a generally circular main region 39 and a generallystraight distal region 40. The proximal region 38 is mounted on theintermediate section 14, as described in more detail below, so that itsaxis is generally parallel to the axis of the intermediate section. Theproximal region 39 preferably has an exposed length, e.g., not containedwithin the intermediate section 14, ranging from about 3 mm to about 12mm, more preferably about 3 mm to about 8 mm, still more preferablyabout 5 mm, but can vary as desired.

[0024] The generally circular main region 39 does not form a flatcircle, but is very slightly helical, as shown in FIGS. 4 to 6. The mainregion 39 has an outer diameter preferably ranging from about 10 mm toabout 25 mm, more preferably from about 12 mm to about 22 mm, still morepreferably about 15 mm. The transition region 41 of the straightproximal region 38 and generally circular main region 39 is slightlycurved and formed such that, when viewed from the side with the proximalregion at the top of the circular man region as shown in FIG. 5, theproximal region (along with the intermediate section 14) forms an angleα with the curved region ranging from about 75° to about 95°, preferablyfrom about 83° to about 93°, more preferably about 87°. The main region39 can curve in a clockwise direction, as shown in FIG. 5, or acounterclockwise direction, as shown in FIG. 6, so that the transitionregion 41 is near the center of the main region, the proximal region(along with the intermediate section 14) forms an angle β with the mainregion ranging from about 90° to about 135°, preferably from about 100°to about 110°, more preferably about 105°.

[0025] The support member 24 is made of a material having shape-memory,i.e., that can be straightened or bent out of its original shape uponexertion of a force and is capable of substantially retuning to itsoriginal shape upon removal of the force. A particularly preferredmaterial for the support member 24 is a nickel/titanium alloy. Suchalloys typically comprise about 55% nickel and 45% titanium. A preferrednickel/titanium alloy is nitinol, which has excellent shape memory,together with ductility, strength, corrosion resistance, electricalresistivity and temperature stability. The non-conductive covering 28can be made of any suitable material, and is preferably made of abiocompatible plastic such as polyurethane or PEBAX.

[0026] A series of ring electrodes 36 are mounted on the non-conductivecovering 28 of the generally circular main region 39 of the mappingassembly 17. The ring electrodes 36 can be made of any suitable solidconductive material, such as platinum or gold, preferably a combinationof platinum and iridium, and mounted onto the non-conductive covering 28with glue or the like. Alternatively, the ring electrodes can be formedby coating the non-covering 28 with an electrically conducting material,kike platinum, gold and/or iridium. The coating can be applied usingsputtering, ion beam deposition or an equivalent technique.

[0027] In a preferred embodiment, each ring electrode 36 is mounted byfirst forming a hole in the non-conductive covering 28. An electrodelead wire 50 is fed through the hole, and the ring electrode 36 iswelded in place over the lead wire and non-conductive covering 28. Thelead wires 50 extend between the non-conductive covering 28 and thesupport member 24. the proximal end of each lead wire 50 is electricallyconnected to a suitable connector 37, which is connected to a source ofRF energy (not shown).

[0028] The number of ring electrodes 36 on the assembly can vary asdesired. Preferably, the number of ring electrodes ranges from about 6to about 20, more preferably from about 8 to about 12. In a particularlypreferred embodiment, the assembly carries 10 ring electrodes. The ringelectrodes 36 are preferably approximately evenly spaced around thegenerally circular main region 39, as best shown in FIG. 7. In aparticularly preferred embodiment, a distance of approximately 5 mm isprovided between the centers of the ring electrodes 36.

[0029]FIGS. 7 and 8 show a particularly preferred electrode arrangement.As explained above, the generally circular main region 39 is veryslightly helical, although FIGS. 7 and 8 depict the main region as aflat circle, as it would generally appear when viewed from the distalend of the catheter. The generally straight distal region 40 forms atangent relative to the generally circular main region 39 and contactsthe main region at a tangent point 43. A first electrode 36 a isprovided, which is the electrode that is on the generally circular mainregion 39 closest to the proximal region 38. A second electrode 36 b isprovided, which is the electrode that is on the generally circular mainregion 39 closest to the distal region 40. Preferably, the firstelectrode 36 a is positioned along the circumference of the generallycircular main region 39 at a distance θ of no more than about 55° fromthe tangent point, more preferably no more than about 48° from thetangent point, still more preferably from about 15° to about 36° fromthe tangent point. Preferably, the second 36 b is position along thecircumference of the generally circular main region 39 at a distance ωof no more than about 55° from the tangent point, more preferably nomore than about 48° from the tangent point, still more preferably fromabout 15° to about 36° from the tangent point. Preferably, the firstelectrode 36 a is positioned along the circumference of the generallycircular main region 39 at a distance γ of no more than 100° from thesecond electrode preferably no more than 80° from the second electrode,still more preferably from about 30° to about 75° from the secondelectrode.

[0030] If desired, additional electrodes (not shown) could be mountedalong the intermediate section 14, the generally straight proximalsection 38, the transition region 41, and the generally straight distalregion 40.

[0031] The generally straight distal region 40 is provided with anatraumatic design to prevent the distal end of the mapping assembly 17form penetrating tissue. In the depicted embodiment, the distal region40 comprises a tightly wound coil spring 44 made, for example, ofstainless steel, such as the mini guidewire commercially available fromCordis Webster (Miami, Fla.) or a coil having a 0.0045 inch wire sizeand a 0.009 inch inner diameter, such as that commercially availablefrom Microspring. The coil spring 44 is mounted at its proximal end in ashort piece of tubing 45 with polyurethane glue or the like, which isthen glued or otherwise anchored within the non-conductive covering 28.The tubing 45 is less flexible than the non-conductive covering 28 butmore flexible than the support member 24 to provide a transition inflexibility along the length of the mapping assembly 17. In the depictedembodiment, the generally straight distal region 40 has a length ofabout 0.5 inch, but can be any desired length, for example, ranging fromabout 0.25 inch to about 1.0 inch. The generally straight distal region40 is preferably sufficiently long to serve as an anchor for introducingthe catheter into a guiding sheath, as discussed in more detail below,because the mapping assembly 17 must be straightened upon introductioninto the sheath. Without having the generally straight distal region 40as an anchor, the mapping assembly 17 has a tendency to pull out of theguiding sheath upon its introduction into the guiding sheath.Additionally, if desired, the distal region 40 can be formed, at leastin part, of a radiopaque material to aid in the positioning of themapping assembly 17 under fluoroscopy.

[0032] The junction of the intermediate section 14 and mapping assembly17 is shown in FIG. 3. The non-conductive covering 28 is attached to thetubing 22 of the intermediate section by glue or the like. The supportmember 24 extends from the third lumen 32into the non-conductivecovering 28. The proximal end of the support member 24 terminates ashort distance within the third lumen 32, about 5 mm, so as not toadversely affect the ability of the intermediate section 14 to deflect.However, if desired, the proximal end of the support member 24 canextend into the catheter body 12.

[0033] The lead wires 50 attached to the ring electrodes 36 extendthrough the first lumen 30 of the intermediate section 14, through thecentral lumen 18 of the catheter body 12, and the control handle 16, andterminate at their proximal end in the connector 37. The portion of thelead wires 50 extending through the central lumen 18 of the catheterbody 12, control handle 16 and proximal end of the intermediate section14 are enclosed within a protective sheath 62, which can be made of anysuitable material, preferably polyimide. The protective sheath 62 isanchored at its distal end to the proximal end of the intermediatesection 14 by gluing it in the first lumen 30 with polyurethane glue orthe like.

[0034] The puller wire 64 is provided for deflection of the intermediatesection 14. The puller wire 64 extends through the catheter body 12, isanchored at its proximal end to the control handle 16, and is anchoredat its distal end to the intermediate section 14. The puller wire 64 ismade of any suitable metal, such as stainless steel or nitinol, and ispreferably coated with Teflon® or the like. The coating impartslubricity to the puller wire 64. The puller wire 64 preferably has adiameter ranging from about 0.006 inch to about 0.010 inch.

[0035] A compression coil 66 is situated within the catheter body 12 insurrounding relation to the puller wire 64. The compression coil 66extends from the proximal end of the catheter body 12 to the proximalend of the intermediate section 14. The compression coil 66 is tightlywound on itself to provide flexibility, i.e., bending, but to resistcompression. The inner diameter of the compression coil 66 is preferablyslightly larger than the diameter of the puller wire 64. The Teflon®coating on the puller wire 64 allows it to slide freely within thecompression coil 66. the outer surface of the compression coil 66 iscovered by a flexible, non-conductive sheath 68, e.g., made of polyimidetubing.

[0036] The compression coil 66 is anchored at its proximal end to theouter wall 20 of the catheter body 12 by proximal glue joint 70 and atits distal end to the intermediate section 14 by distal glue joint 72.Both glue joints 70 and 72 preferably comprise polyurethane glue or thelike. The glue may be applied by means of a syringe or the like througha hole made between the outer surface of the catheter body 12 and thecentral lumen 18. Such a hole may be formed, for example, by a needle orthe like that punctures the outer wall 20 of the catheter body 12 whichis heated sufficiently to form a permanent hole. The glue is thenintroduced through the hole to the outer surface of the compression coil66 and wicks around the outer circumference to form a glue joint aboutthe entire circumference of the compression coil.

[0037] The puller wire 64 extends into the second lumen 32 of theintermediate section 14. Preferably the puller wire 64 is anchored atits distal end to the distal end of the intermediate section 14, asshown in FIG. 3. Specifically, a T-shaped anchor is formed, whichcomprises a short piece of tubular stainless steel 80, e.g., hypodermicstock, which is fitted over the distal end of the puller wire 64 andcrimped to fixedly secure it to the puller wire. The distal end of thetubular stainless steel 80 is fixedly attached, e.g., by welding, to across-piece 82 formed of stainless steel ribbon or the like. Thecross-piece 82 sits beyond the distal end of the second lumen 32. Thecross-piece 82 is larger than the lumen opening and, therefore, cannotbe pulled through the opening. The distal end of the second lumen 32 isthen filled with glue or the like. Preferably a polyurethane glue.Within the second lumen 32 of the intermediate section 14, the pullerwire 64 extends through a plastic, preferably Teflon®, puller wiresheath (not shown), which prevents the puller wire 64 from cutting intothe wall of the intermediate section 14 when the intermediate section isdeflected.

[0038] Longitudinal movement of the puller wire 64 relative to thecatheter body 12, which results in deflection of the intermediatesection 14, is accomplished by suitable manipulation of the controlhandle 16. Examples of suitable control handles for use in the presentinvention are disclose, for example, in U.S. Pat. Nos. Re 34,502 and5,897,529, the entire disclosures of which are incorporated herein byreference.

[0039] In use, a suitable guiding sheath is inserted into the patientwith its distal end positioned at a desired mapping location. An exampleof a suitable guiding sheath for use in connection with the presentinvention is the Preface™ Guiding Sheath, commercially available fromCordis Webster (Diamond Bar, Calif). The distal end of the sheath isguided into one of the atria. A catheter in accordance with the presentinvention is fed through the guiding sheath until its distal end extendsout of the distal end of the guiding sheath. As the catheter is fedthrough the guiding sheath, the mapping assembly 17 is straightened tofit through the sheath. Once the distal end of the catheter ispositioned at the desired mapping location, the guiding sheath is pulledproximally, allowing the deflectable intermediate section 14 and mappingassembly 17 to extend outside the sheath, and the mapping assembly 17returns to its original shape due to the shape-memory of the supportmember 24. The mapping assembly 17 is then inserted onto a pulmonaryvein or other tubular region (such as the coronary sinus, superior venacave, or inferior vena cava) so that the outer circumference of thegenerally circular main region 39 of the assembly is in contact with acircumference inside the tubular region. Preferably, at least about 50%,more preferably at least about 70%, and still more preferably at leastabout 80% of the circumference of the generally circular main region isin contact with a circumference inside the tubular region.

[0040] The circular arrangement of the electrodes 36 permits measurementof the electrical activity at that circumference of the tubularstructure so that ectopic beats between the electrodes can beidentified. The size of the generally circular main region 39 permitsmeasurement of electrical activity along a diameter of a pulmonary veinor other tubular structure of or near the heart because the circularmain region has a diameter generally corresponding to that of apulmonary vein or the coronary sinus. Additionally, because the mainregion 39 preferably does not form a flat circle, but instead issomewhat helical, as shown in FIG. 4, it is easier for the user to guidethe mapping assembly 17 into a tubular region.

[0041] If desired, two or more puller wires can be provided to enhancethe ability to manipulate the intermediate section. In such anembodiment, a second puller wire and a surrounding second compressioncoil extend through the catheter body and into an additional off-axislumen in the intermediate section. The first puller wire is preferablyanchored proximal to the anchor location of the second puller wire.Suitable designs of catheters having two or more puller wires, includingsuitable control handles for such embodiment, are described, forexample, in U.S. patent application Ser. No. 08/924.611, filed Sep. 5,1997; Ser. No. 09/130,359, filed Aug. 7, 1998; Ser. No. 09/143,426,filed Aug. 28, 1998; and Ser. No. 09/157.055, filed Sep. 18, 1998,disclosures of which are incorporated herein by reference.

[0042] The preceding description has been presented with reference topresently preferred embodiments of the invention. Workers skilled in theart and technology to which this invention pertains will appreciate thatalterations and changes in the described structure may be practicedwithout meaningfully departing from the principal, spirit and scope ofthis invention.

[0043] Accordingly, the foregoing description should not be read aspertaining only to the precise structures described and illustrated inthe accompanying drawings, but rather should be read consistent with andas support for the following claims which are to have their fullest andfairest scope.

What is claimed is:
 1. A mapping catheter comprising: an elongatedtubular catheter body having an outer wall, proximal and distal ends,and at least one lumen extending therethrough; and a mapping assemblycomprising: a tubular structure having a generally straight proximalregion attached to the catheter body, a generally circular main regiongenerally transverse and distal to the proximal region having an outercircumference, a transition region connecting the proximal region andthe main region, and a generally straight distal region distal the mainregion and extending substantially tangentially from the main region,wherein the tubular structure comprises a non-conductive cover over atleast the main region of the mapping assembly, a support member havingshape-memory disposed within at least the main region of the mappingassembly; and a plurality of spaced-apart electrodes carried by thegenerally circular main region of the mapping assembly.
 2. A catheteraccording to claim 1, further comprising an intermediate section betweenthe catheter body and the mapping assembly, the intermediate sectionhaving at least one lumen extending therethrough and being more flexiblethan the catheter body.
 3. A catheter according to claim 2, wherein theintermediate section has three lumens extending therethrough.
 4. Acatheter according to claim 1, wherein the generally circular mainregion has an outer diameter ranging from about 10 mm to about 25 mm. 5.A catheter according to claim 1, wherein the generally circular mainregion has an outer diameter ranging from about 10 mm to about 25 mm. 6.A catheter according to claim 1, wherein the generally circular mainregion ha n outer diameter of about 15 mm.
 7. A catheter according toclaim 1, wherein the transition region is slightly curved and formedsuch that, when viewed from the side of the catheter with the proximalregion at the top of the circular main region, the proximal region formsan angle a with the circular region ranging from about 75° to about 95°.8. A catheter according to claim 1, wherein the transition region isslightly curbed and formed such that, when viewed from the side of thecatheter with the proximal region at the top of the circular mainregion, the proximal region forms an angle a with the circular mainregion ranging from about 83° to about 93°.
 9. A catheter according toclaim 1, wherein the number of electrodes along the generally circularmain region ranges from about 6 to about
 20. 10. A catheter according toclaim 1, wherein the number of electrodes along the generally circularmain region ranges from about 8 to about
 12. 11. A catheter according toclaim 1, wherein the electrodes are approximately evenly spaced aroundthe generally circular main region.
 12. A catheter according to claim 1,wherein the generally straight proximal region has an exposed lengthranging from about 3 mm to about 12 mm.
 13. A catheter according toclaim 1, wherein the generally straight proximal region has an exposedlength ranging from about 3 mm to about 8 mm.
 14. A catheter accordingto claim 1, wherein the generally straight distal region has anatraumatic design to prevent the distal end of the mapping assembly frompenetrating tissue.
 15. A catheter according to claim 1, wherein thegenerally straight distal region has a length ranging from about 0.25inch to about 1.0 inch.
 16. A catheter according to claim 2, furthercomprising a control handle mounted at the proximal end of the catheterbody and means for deflecting the intermediate section by manipulationof the control handle.
 17. A catheter according to claim 16, wherein thecontrol handle comprises a first member fixedly attached to the proximalend of the catheter body and a second member that is movable relative tothe first member.
 18. A catheter according to claim 17, wherein thedeflecting means comprises a puller wire having a proximal end and adistal end, the puller wire extending from the control handle, throughthe catheter body and into a lumen in the intermediate section, whereinthe distal end of the puller wire is fixedly secured within theintermediate section and the proximal end of the puller wire is fixedlysecured to the second member of the control handle, whereby manipulationof the first member of the control handle relative to the second memberof the control handle moves the puller wire relative to the catheterbody, resulting in deflection of the intermediate section.
 19. A mappingcatheter comprising: an elongated tubular catheter body having an outerwall, proximal and distal ends, and at least one lumen extendingtherethrough; and a mapping assembly comprising: a tubular structurecomprising a generally circular main region generally transverse anddistal to the catheter body and having an outer circumference and agenerally straight distal region distal to the main region extendingsubstantially tangentially from the generally circular main region andgenerally transversally to the catheter body, wherein the tubularstructure comprises a non-conductive cover over at least the main regionof the mapping assembly; a support member having shape-memory disposedwithin at least the main region of the mapping assembly; and at leastone electrode carried by the generally circular main region of themapping assembly.
 20. A catheter according to claim 19, wherein themapping assembly further comprises a generally straight proximal regionattached to the catheter body and a transition region connecting theproximal region and the main region.
 21. A catheter according to claim19, wherein the mapping assembly comprises a plurality of electrodescarried by the generally circular main region of the mapping assembly,wherein the electrodes are generally evenly spaced about the entirecircumference of the mapping assembly such that, in use, when themapping assembly is positioned in a tubular region of or near the heart,with the outer circumference of the generally circular main region incontact with the inner circumference of the tubular region, theelectrodes can be used to map the inner circumference of the tubularregion.
 22. A catheter according to claim 19, wherein the generallycircular main region has an outer diameter ranging from about 10 mm toabout 25 mm.
 23. A catheter according to claim 19, wherein the generallycircular main region has an outer diameter ranging from about 12 mm toabout 20 mm.
 24. A catheter according to claim 19, wherein the number ofelectrodes along the generally circular main region ranges from about 6to about
 20. 25. A catheter according to claim 19, wherein the number ofelectrodes along the generally circular main region ranges from about 8to about
 12. 26. A catheter according to claim 19, wherein the generallystraight distal region has an atraumatic design to prevent the distalend of the mapping assembly from penetrating tissue.
 27. A catheteraccording to claim 19, further comprising means for deflecting thedistal end of the catheter body without altering the shape of themapping assembly.
 28. A catheter according to claim 27, wherein thedeflecting means comprises: a puller wire extending through a lumen ofthe catheter body, said puller wire being fixedly attached at its distalend to the catheter body near the catheter body's distal end; and acontrol handle for moving the puller wire longitudinally relative to thecatheter body to thereby cause deflection of the distal end of thecatheter body.
 29. A catheter according to claim 19, wherein the distalregion is more flexible than the main region.
 30. A mapping cathetercomprising: an elongated tubular catheter body having an outer wall,proximal and distal ends, and at least one lumen extending therethrough;a mapping assembly comprising: a tubular structure having a generallycircular main region generally transverse and distal to the catheterbody having an outer circumference, and a generally straight distalregion distal to the main region extending substantially tangentiallyfrom the generally circular main region, wherein the tubular structurecomprises a non-conductive cover over at least the main region of themapping assembly; a support member having shape-memory disposed withinat least the main region of the mapping assembly; and at least oneelectrode carried by the generally circular main region of the mappingassembly; and means for deflecting the distal end of the catheter bodywithout altering the shape of the mapping assembly.
 31. A catheteraccording to claim 30, wherein the deflecting means comprises: a pullerwire extending through a lumen of the catheter body, said puller wirebeing fixedly attached at its distal end to the catheter body near thecatheter body's distal end; and a control handle for moving the pullerlongitudinally relative to the catheter body to thereby cause deflectionof the distal end of the catheter body.
 32. A catheter according toclaim 30, wherein the generally circular main region has an outerdiameter ranging form about 10 mm to about 25 mm.
 33. A catheteraccording to claim 30, wherein the generally circular main region has anouter diameter ranging from about 12 mm to about 20 mm.
 34. A catheteraccording to claim 30, wherein the number of electrodes along thegenerally circular main region ranges from about 8 to about
 12. 35. Acatheter according to claim 30, wherein the mapping assembly comprises aplurality of electrodes carried by the generally circular main region ofthe mapping assembly, wherein the electrodes are generally evenly spacedabout the entire circumference of he mapping assembly such that, in use,when the mapping assembly is positioned in a tubular region of or nearthe heart, with the outer circumference of the generally circular mainregion in contact with the inner circumference of the tubular region,the electrodes can be used to map the inner circumference of the tubularregion.
 36. A catheter comprising: an elongated flexible tubularcatheter body having an axis and proximal and distal ends; a mappingassembly at the distal end of the tubular body having a preformedgenerally circular curve having an outer surface and being generallytransverse to the axis of the catheter body, the mapping assembly alsohaving a proximal end, and a generally straight distal end distal to thegenerally circular curve and extending substantially tangentiallytherefrom, the mapping assembly carrying a plurality of spaced apartelectrodes; an electrode lead wire associated with each electrode, eachelectrode lead wire having proximal and distal ends and extendingthrough the catheter body and into the mapping assembly, the distal endof each electrode lead wire being electrically connected to itsassociated electrode; a puller wire having proximal and distal endsextending through the tubular catheter body, the distal end of thepuller wire being fixedly attached to the distal end of the catheterbody; and a handle connected to the proximal ends of the catheter bodyand puller wire for moving the puller wire longitudinally relative tothe catheter body, whereby longitudinal movement of the puller wirerelative to the catheter body results in deflection of the distal end ofthe catheter body.
 37. A catheter according to claim 36, wherein theelectrodes carried by the generally circular curve are generally evenlyspaced about the generally circular curve of the mapping assembly, suchthat, in use, when the generally circular curve is positioned in atubular region of or near the heart, with the outer surface of thegenerally circular curve in contact with the inner circumference of thetubular region, the electrodes can be used to map the innercircumference of the tubular region.
 38. A catheter according to claim36, wherein the generally circular curve has an outer diameter rangingfrom about 10 mm to about 25 mm.
 39. A catheter according to claim 36,wherein the generally circular curve has an outer diameter ranging fromabout 12 mm to about 20 mm.
 40. A catheter according to claim 36,wherein the distal region is more flexible than the generally circularcurve.
 41. A mapping catheter comprising: an elongated flexible tubularcatheter body having an axis and proximal and distal ends; a mappingassembly at the distal end of the tubular body comprising a compoundcurve having a first bend away from the axis of the catheter body and asecond bend having a preformed generally circular curve transverse tothe axis of the catheter body, said mapping assembly having a proximalend, and a generally straight distal end extending substantiallytangentially from the generally circular curve and generallytransversally to the axis of the catheter body, the mapping assemblycarrying a plurality of spaced apart electrodes; an electrode lead wireassociated with each electrode, each electrode lead wire having proximaland distal ends and extending through the catheter body and into themapping assembly, the distal end of each electrode lead wire beingelectrically connected to its associated electrode; a puller wire havingproximal and distal ends extending through the tubular catheter body,the distal end of the puller wire being fixedly attached to the distalend of the catheter body; and a handle connected to the proximal ends ofthe catheter body and puller wire for moving the puller wirelongitudinally relative to the catheter body, whereby longitudinalmovement of the puller wire relative to the catheter body results indeflection of the distal end of the catheter body.
 42. A catheteraccording to claim 41, wherein the compound curve has an outer diameterranging from about 10 mm to about 25 mm.
 43. A catheter according toclaim 41, wherein the compound curve has an outer diameter ranging fromabout 12 mm to about 20 mm.
 44. A catheter according to claim 41,wherein the number of electrodes on the mapping assembly ranges fromabout 8 to about
 12. 45. A catheter according to claim 41, wherein thedistal region is more flexible than the compound curve.
 46. A catheteraccording to claim 41, wherein the generally straight distal region ismore flexible than the compound curve.
 47. A mapping cathetercomprising: an elongated tubular catheter body having an outer wall,proximal and distal ends, and at least one lumen extending therethrough;and a mapping assembly comprising: a tubular structure comprising agenerally circular main region generally transverse and distal to thecatheter body and having an outer circumference and a generally straightdistal region distal to the main region extending substantiallytangentially from the generally circular main region, the distal regionbeing more flexible than the generally circular main region, wherein thetubular structure comprises a non-conductive cover over at least themain region of the mapping assembly; a support member having shapememory disposed within at least the main region of the mapping assembly;and at least one electrode carried by the generally circular main regionof the mapping assembly.
 48. A catheter according to claim 47, whereinthe mapping assembly further comprises a generally straight proximalregion attached to the catheter body and a transition region connectingthe proximal region and the main region.
 49. A catheter according toclaim 47, wherein the generally circular main region has an outerdiameter ranging from about 10 mm to about 25 mm.
 50. A catheteraccording to claim 47, wherein the generally circular main region has anouter diameter ranging from about 12 mm to about 20 mm.
 51. A catheteraccording to claim 47, wherein the number of electrodes along thegenerally circular main region ranges from about 8 to about
 12. 52. Amapping catheter comprising: an elongated tubular catheter body havingan outer wall, proximal and distal end, and at least on lumen extendingtherethrough; and a mapping assembly comprising: a tubular structurecomprising a generally circular main region generally transverse anddistal to the catheter body and having an outer circumference and adiameter ranging from about 10 mm to about 25 mm, and a generallystraight distal region distal the main region extending substantiallytangentially relative to the generally circular main region, wherein thetubular structure comprises a non-conductive cover over at least themain region of the mapping assembly; a support member having shapememory disposed within at lest the main region of the mapping assembly;a plurality of electrodes carried by the generally circular main regionof the mapping assembly; and a plurality of electrode lead wires, eachelectrode lead wire having a distal end electrically connected to acorresponding electrode on the generally circular main region and aproximal end electrically connected to a suitable monitoring apparatus.53. A catheter according to claim 52, wherein the generally circularmain region has an outer diameter ranging from about 12 mm to about 20mm.
 54. A catheter according to claim 52, wherein the number ofelectrodes along the generally circular main region ranges from about 8to about
 12. 55. A catheter according to claim 52, wherein the distalregion is more flexible than the main region.
 56. A mapping cathetercomprising: an elongated tubular catheter body having an outer wall,proximal and distal ends, and at least one lumen extending therethrough;and a mapping assembly comprising: a tubular structure comprising agenerally circular main region generally transverse and distal to thecatheter body and having an outer circumference and a diameter rangingfrom about 10 mm to about 25 mm, and a generally straight distal regiondistal to the main region extending substantially tangentially relativeto the generally circular main region; a plurality of electrodes carriedby the generally circular main region of the mapping assembly; and aplurality of electrode lead wires, each electrode lead wire having adistal end electrically connected to a corresponding electrode on thegenerally circular main region.
 57. A catheter according to claim 56,wherein, when the catheter is viewed from the side with the catheterbody positioned at the top of the generally circular main region, thecatheter body forms an angle with the generally circular main regionranging from about 75° to about 95°.
 58. A catheter according to claim56, wherein, when the catheter is viewed from the side with the catheterbody positioned at the top of the generally circular main region, thecatheter body forms an angle with the generally circular main regionranging from about 83° to about 93°.
 59. A catheter according to claim56, wherein the generally circular main region has an outer diameterranging from about 12 mm to about 20 mm.
 60. A catheter according toclaim 56, wherein, when the catheter is viewed from the side with thecatheter body positioned at the top of the generally circular mainregion, the catheter body forms an angle with the generally circularmain region ranging from about 75° to about 95°.